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Heifer age at conception tended to be linearly associated with sex ratio of single calves: from 45(male):55(female) at 14 months to 60:40 at 19 months. A 14% reduction in the value of calves from heifers could occur over this range at a heifer:bull calf price ratio of 3:1.

Sex ratio of single calves born to multiparous cows tended to increase linearly from 53:47 to 57:43 as number of inseminations increased from 1 to 5. This result suggested that cows in better body condition produced a higher proportion of bull calves, and could represent a 4% reduction in the value of their calves.